Published Date: 2003-01-17 23:50:00
Subject: PRO/AH> Corynebacterium, equine - USA (Kentucky) (03)
Archive Number: 20030117.0143
CORYNEBACTERIUM, EQUINE - USA (KENTUCKY) (03)
*********************************
A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail, a program of the
International Society for Infectious Diseases
<http://www.isid.org>
Date: 16 Jan 03
From: Fabio Del Piero <fdp@vet.upenn.edu>
You recently speculated that a recent increase of equine cases of
corynebacterium infection may be associated with interference with and/or
an impairment of the immune system by West Nile flavivirus infection. With
no disrespect intended, my previous response to this speculation was that
there is no evidence of WNV colonizing equine organs of the immune system
and interfering with their normal function.
The response to my statement was that our early publications (Snook et al,
2001; Cantile et al, 2001) reporting WNV equine infections in 1999-2001
were, perhaps, somehow dated and that the virus had since mutated in such a
way as to allow effects on the immune system, allowing for infection, such
as _Corynebacterium_, to occur, all of this in horses without clinical
evidence of WNV infection. Perhaps one of the most direct way to answer the
question is to have the horses affected with _Corynebacterium_ tested for
WNV infection.
However, our (as yet unpublished) findings after evaluating equine WNV
infection during the most recent season (summer and fall of 2002) were
consistent with our previous findings: the WNV cellular colonization
appears to be limited to the central nervous system (CNS) only (cytoplasm
of glial cells, neurons, and fibers) with no involvement of immune system
organs such as spleen, lymph nodes, laryngeal lymphoid follicles,
gastrointestinal lymphoid tissue, cutaneous dendritic cells, hepatic
Kupffer cells, and renal interstitial dendritic cell populations.
We perform complete necropsies on WNV cases at our facility. None of the
WNV infected horses observed by our faculty and staff clinicians (horses
that survived, died, or were unfortunately euthanized because of their
severe and irreversible neurological deficit) presented evidence of
concomitant secondary infections with other viruses, bacteria, protozoa,
mycetes, yeasts, or protista. Not one of these horses later presented with
some unusual enhanced predisposition to any of the etiologic agents
mentioned above. Neither did the pathologists involved in the postmortem
examinations of WNV infected horses identify other concomitant infections,
only the microscopic lesions caused by WNV within brainstem and spinal cord.
To my knowledge, even in other arboviral infections inducing
encephalomyelitis in horses, there is no evidence of concomitant infections
or short/long-term impairment of the immune system. As an example, eastern
equine encephalitis alphavirus, in vivo, is able to colonize extraneural
cells in horses, in particular circulating macrophages, neutrophils, and
interstitial renal dendritic cells, but no secondary infections are
observed (Del Piero et al, 2001; Del Piero et al, unpublished).
Equine herpesvirus 1 (EHV1), equine arteritis arterivirus, and equine
influenza orthomyxoviruses are, in some cases, able to predispose to
secondary bacterial cranioventral bronchopneumonia. The EHV1 ischemic
myelopathy, characterized by vascular, non-neuronal, viral infection of CNS
vascular endothelia, myocytes, and pericytes is not associated with
secondary infections. All the viruses above extensively colonize lymphoid
organs, where they also induce cell necrosis. Regarding WNV infection in
other species, as described very well by others (Steele et al, 1999), we
recognize multisystemic cellular polytropism of the virus in birds,
sometimes with secondary opportunistic infection such as bacterial
enteritis and mycotic pneumonia in some avian species. If we see a
different pattern in the equine cases during the upcoming WNV seasons, we
will bring it to the attention of ProMED-mail.
Cantile C, Del Piero F, Di Guardo G, et al. Pathologic and
immunohistochemical findings in naturally occurring West Nile virus
infection in horses. Vet Pathol 2001; 38: 414-21.
Snook CS, Hyman SS, Del Piero F, et al. West Nile virus encephalomyelitis
in eight horses. J Am Vet Med Assoc 2001; 218: 1576-9.
Del Piero F, Wilkins PA, Dubovi EJ, et al. Clinical, pathologic,
immunohistochemical, and virologic findings of eastern equine
encephalomyelitis in two horses. Vet Pathol 2001;38: 451-6.
Steele KE, Linn MJ, Schoepp RJ, et al. Pathology of fatal West Nile virus
infections in native and exotic birds during the 1999 outbreak in New York
City, New York. Vet Pathol 2000;37: 208-24.
--
Fabio Del Piero
Diplomate American College of Veterinary Pathologists
University of Pennsylvania
School of Veterinary Medicine
New Bolton Center
Department of Pathobiology
Department of Clinical studies
Philadelphia - Kennett Square
PA, USA
<fdp@vet.upenn.edu>
[Dr Del Piero has presented a nice explanation why of my speculation was in
error. Thank you for your excellent reply. - Mod.TG]
See Also
Corynebacterium, equine - USA (Kentucky) (02) 20030112.0104Corynebacterium, equine - USA (Kentucky) 20030111.0096
Corynebacterium, equine - USA (Colorado) 20030110.0085
2002
---
Corynebacterium, equine - USA (Wyoming) 20021125.5895
......................tg/pg/sh
*##########################################################*
ProMED-mail makes every effort to verify the reports that
are posted, but the accuracy and completeness of the
information, and of any statements or opinions based
thereon, are not guaranteed. The reader assumes all risks in
using information posted or archived by ProMED-mail. ISID
and its associated service providers shall not be held
responsible for errors or omissions or held liable for any
damages incurred as a result of use or reliance upon posted
or archived material.
************************************************************
Visit ProMED-mail's web site at <http://www.promedmail.org>.
Send all items for posting to: promed@promedmail.org
(NOT to an individual moderator). If you do not give your
full name and affiliation, it may not be posted. Send
commands to subscribe/unsubscribe, get archives, help,
etc. to: majordomo@promedmail.org. For assistance from a
human being send mail to: owner-majordomo@promedmail.org.
############################################################
############################################################